[PATCH] D15969: [WebAssembly] Don't create a needless .note.GNU-stack section

[Dan Gohman via llvm-commits]

sunfish updated this revision to Diff 45027.
sunfish added a comment.

Use a bool flag that is set by the constructor instead of a virtual function, as requested by Rafael.


Repository:
  rL LLVM

http://reviews.llvm.org/D15969

Files:
  include/llvm/MC/MCAsmInfoELF.h
  lib/MC/MCAsmInfoELF.cpp
  lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCAsmInfo.cpp

Index: lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCAsmInfo.cpp
===================================================================
--- lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCAsmInfo.cpp
+++ lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCAsmInfo.cpp
@@ -48,4 +48,7 @@
   ExceptionsType = ExceptionHandling::None;
 
   // TODO: UseIntegratedAssembler?
+
+  // WebAssembly's stack is never executable.
+  UsesNonexecutableStackSection = false;
 }
Index: lib/MC/MCAsmInfoELF.cpp
===================================================================
--- lib/MC/MCAsmInfoELF.cpp
+++ lib/MC/MCAsmInfoELF.cpp
@@ -21,12 +21,15 @@
 void MCAsmInfoELF::anchor() { }
 
 MCSection *MCAsmInfoELF::getNonexecutableStackSection(MCContext &Ctx) const {
+  if (!UsesNonexecutableStackSection)
+    return nullptr;
   return Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0);
 }
 
 MCAsmInfoELF::MCAsmInfoELF() {
   HasIdentDirective = true;
   WeakRefDirective = "\t.weak\t";
   PrivateGlobalPrefix = ".L";
   PrivateLabelPrefix = ".L";
+  UsesNonexecutableStackSection = true;
 }
Index: include/llvm/MC/MCAsmInfoELF.h
===================================================================
--- include/llvm/MC/MCAsmInfoELF.h
+++ include/llvm/MC/MCAsmInfoELF.h
@@ -18,6 +18,10 @@
   MCSection *getNonexecutableStackSection(MCContext &Ctx) const final;
 
 protected:
+  /// Targets which have non-executable stacks by default can set this to false
+  /// to disable the special section which requests a non-executable stack.
+  bool UsesNonexecutableStackSection;
+
   MCAsmInfoELF();
 };
 }


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